Photographic process



Fetented Feb. 27, 1945 rno'rocaarmo PnocEss Kenneth Smith-Minneapolis, Minn and Rudolph Zerbst,Wechawken, N. 1., asslgnors to Scrlver, Smith & Zerbst, Incorporated, a corporation of a Minnesota No Drawing. Application August 7, 1941,

Serial No. 405,802

9laims.

It is an object of this invention to provide anovel process whereby protographic images are fortified and given depth and durability by deposits of non-fading, wear-resistant pigment so distributed as to reproduce all of the delicate tones of the subject.

Another subject is to provide photographic reproductions on various durable materials without the use of half tone screens or any etching procedure.

A further object is to provide a novel and inexpensive procedure for decorating and marking metals, plastics and other heat fusible materials whereby the decoration or marking is fused with the body of material or caused to penetrate the surface sufiloiently to impart a high degree of wear resistance.

Qther ob ects will appear and be more fully rial to be decorated has an irregular, curved or undulated surface to be decorated or Wheareirom the size or nature of the object to be decorated the reproduction can best be developed on a separate plate and thereafter transferred to and bonded with the object. Our procedure is further varied according to the degree of wearresistance desired and thenature of the material,

on which the subject is reproduced.

Whether the subject is to be reproduced directly on the object to be decorated or on a separate plate, We utilize in one of the early steps of our process a sensitizing solution which, when partially dried, is an adhesive of such character that it is rendered less adhesive or tacky in pro-.

portion to its exposure to sunlight or to suitable artificial light, the solution containing one or more constituents which are rendered insoluble by exposure to such light. Our preferred solution sium bi-chromate and ammonia in the approximate proportions by volume of:

Parts Dextrin 1 Glucose 4 Glycerine 1' Potassium bi-chromate 1 /2 Ammonia solution (10%) 1 Water 44 strong light containing ultra-violet rays should be avoided but it is not so sensitive as'to require that the work of applying it be carried out in a dark room and our improved process has the advantage of permitting all operations to be per-- 7 formed indoors in ordinary natural or artificial ately low and substantially uniform humidity quires about 20 minutes, more or less, depending light. For best results in most climates the work room should be air conditioned so that moderis maintained. a

To reproduce a photograph or drawing on a flat plate from which the reproduction may be transferred to the object to be decorated, we first thoroughly cleanse a fiat piece of plate glass or other smooth material. It is then given a coa ing of our sensitizing solution, hereinbefore described, placed in a drip rack and allowed to dry until the sensitized surface has become tacky to the touch. This drying is hastened by placing the plate in an oven the temperature, of which is maintained at approximately 125 degrees Fahrenheit. Ordinarily such oven drying reon atmospheric conditions. When the sensitized surface has become tacky to the touch, the plate is placed in a printing frame together with the photographic negative or transparent positive of the subject. the latter being placed in contact with the tacky side of the plate. As the next step the subjectis reproduced photographically on the plate by exposure to an are light, the length of exposure depending on the density of the photographic negative or positive. The peis an aqueous solution of dextrin, glucose, potasonds with a carbon are light of 35,000 foot candlepower. Otherwise the image may be reproduced by the use of a prQJectorcontaimng the negative or positive film and the image may be enlarged or reduced in conventional manner.

After exposure, the sensitized plate is removed from the printing frame and the exposed tacky surace is covered with a dry, pulverized ceramic of the desired color or with finely ground silver, gold or other metal or coloring material. The

pigment or coloring powder must be capable of' withstanding the degree of heat to which itvis subjected in the treatment hereinafter described. The excess pigment is maining forms the desired image. The amount of pigment which adheres to the image at any given point is proportional to the density of the subject at the corresponding point, with the result that all of the delicate tones of the subject are reproduced and the entire image is given increased body and definition. This result is obtained due to the fact that our sensitizing solution loses its adhesiveness or tacky character in proportion to its exposure to light, so that after exposure the pigment adheres to the lesser exposed areas with greater density than it does to the more exposed areas.

The plate with the image thus fortified is now given a coat of suitable lacquer and allowed to dry. Our preferred lacquer is made according to the following formula:

Per cent Nitrocellulose l Dibutyl phthala China-wood oil Butyl acetate Butyl alcohol 20 Toluol 40 When the lacquer coated plate has thoroughly dried, it is placed in a bath of water and allowed to soak until the film of pigment and lacquer can be readily lifted from the sensitizedplate. It will be understood that the excess sensitizing solution which has not been rendered insoluble by exposure to light is washed out by the bath and this frees the pigment and lacquer image from the plate. Removal of this film-like image from the bath is facilitated by using a sheet of paper which is superimposed on the image in the bath and used as a support or backing to transfer the image to the object to be decorated.

As the next step, the object to be decorated, whether of metal, plastic, glass or other material is coated with an adhesive, preferably of water-resistant type such as casein glue, The image with its lacquer binder is now transferred to and superimposed upon the adhesive coated surface of the object to be decorated and is pressed down firmly, in proper position thereon. The pigment of the image, being bound by the flexible lacquer, is sufficiently flexible to take the shape of the object to be decorated whether it be concave, convex, angular or irregular. The adhesive is allowed to dry and then the lacquer binder is removed by applying a suitable solvent therefor. For the lacquer hereinbefore .described a solvent containing the following constituents may be employed:

Per cent Toluen 50 Butyl alcohol 16% Ethyl ace 16% Butyl aceta 16% Such a solvent removes the lacquer without affecting the pigment of the image which is held in place by the adhesive.

Our further treatment to, impart a maxi-,

brushed off and that redecoration or marking on metal, plastic or certain other heat fusible materials is as follows: The object with the pigment film adhered thereto as hereinbefore described is placed in a kiln and is heated to a-temperature and for such period of time as may be required to produce fusion of the pigment film with the supporting surface. When the object to be decorated is composed of metal or certain other materials which are reactive to oxygen in the kiln, the latter should be supplied with an inert gas, such as nitrogen, to avoid the discoloration or other objectionable reaction with oxygen. By properly regulating the degree of heat and duration of the treatment, the film of pigment is caused to penetrate the supporting surface and to become an integral part of the object. Some examples of suitable temperatures and durations of heat treatment for various metals are here given by way of example.

With either a silver decoration on a gold object or a gold decoration on a silver object, a temperature of approximately 1725 degrees Fahrenheit maintained for a period of approximately two minutes is sufficient to produce the desired result. A like temperature and period of heat treatment is satisfactory where the decoration is formed by a powdered ceramic color on silver. A slightly higher temperature, or approximately 1760 degrees F. for two minutes, is preferable to unite a ceramic design with a gold object. Where a stainless steel object is to be decorated with a ceramic pigment, a temperature equal to approximately 2350 degrees F. should be maintained for approximately four minutes while in the case of a ceramic on a copper object a temperature of 1560 degrees 1'. may be maintained for one and one-half minutes.

In cases where the object to be decorated has a fiat, smooth surface on which the image may be formed directly, we eliminate the foregoing steps involving the use of a separate plate. According to our simplified procedure, the area to be decorated is first thoroughly cleansed of any dirt, grease or other foreign matter and i given a coating of our sensitizing solution. The work is then placed in a drip rack and allowed to partially dry in a dust-free atmosphere. The drying is preferably carried out in an oven, the temperature of which is maintained at approximately degrees Fahrenheit for a period of time sufiicient to render the sensitized surface tacky to the touch.

The next procedure is similar to that hereinbefor described in that the image of the photograph or drawing is projected onto the sensitized and tacky surface by the use of an arc light, the period of the exposure depending on the density of the negative or transparent positive and the intensity of the light. A faintly perwater bath to remove the soluble residue of the sensitizing solution, care being taken to avoid removing or disturbing the pigment. Upon removal from the bath the work is allowed to dry.

The subsequent treatment is dependent upon the nature of the material from which the object is made and the degree of durability desired. Where maximum durability is desired, the object with the film of pigment forming the imagr thereon is placed in a kiln and is heat treated to cause the image to fuse and penetrate the surface of the object. This has the effect of permanently uniting the decoration to the supporting material where the latter is of such character as to be fusible at the temperature attained, as more fully hereinbefore described.

In cases where maximum durability is not required, thefilm of pigment forming the image on the object to be decorated is given a coat of clear synthetic resin and is baked in an oven for a suflicient period to form a hard, durable coating over the pigment. We have found that excellent wearing qualities are imparted to the pigment on objects of metal and numerous other materials when a synthetic resin of the ureaformaldehyde type is used as the finishing coat. This permeates the film of pigment and when baked forms a strong, flexible bond between the pigment and supporting material and also between the particles of pigment. If a low bakin temperature is desirable such a resin may be baked for a period of two hours at a temperature of approximately 180 degrees Fahrenheit to impart adequate durability to the work. Where the material from which the object is constructed will withstand higher temperatures, the resin coated work may be treated at a higher temperature and for a shorter period of time. For example, the baking rnay be conducted at 2.50 degrees Fahrenheit for one hour, or 300=degrees Fahrenheit for one-quarter hour, or at 400 degrees for five minutes.

By appropriate modification of the degree and duration of the heat treatment,'our process may be applied to numerous synthetic and other modern composition materials and to surfaces of mother-of-pearl, tortoise shell, bone, wallboard, linoleum, glass and vitreous enameled metals. In all cases the protrusion of our film of pigment or coloring matter from the surface is so slight that it does not wear off at the higher or denser spots first, as is the case where the decoration has been formed by the silk screen process or hand decorating.

Where less durable decoration will meet the requirements, the baking of the work may be dispensed with and after allowing our film of pigment to dry in contact with the adhesive on the object we give the decorated area a coat of any suitable clear lacquer and allow it to dry.

Our process has many fields of utility, including the marking and decoration of silver, gold and platinum ware, reproduction of portraits in miniature on precious metal plates. the decoration of costume jewelry, placing of insignia on exterior metal surfaces of airplanes, the decoration of interior walls constructed from metal and other materials, the decoration of plastic receptacles and tableware and the accurate reproduction of drawings and permanent marking on metal parts of airplanes and other machines in the manufacture thereof.

Having described our invention, what we claim as new and desire to protect by Letters Patent is:

1. The process which comprises coating a surface with alight sensitive solution containing the following constituents in approximately the proportions by volume of:

Parts Parts Dextrine l Bichromate 1 Glucose 4 Water 44 Glycerine 1 then evaporating the bulk of the water, projecting on the tacky area thus formed an image of the subject so as to harden the area of the'coating at various points in proportion to the exposure of the same to light, then depositing apigment on the projected image and causin the pigment to adhere at various points thereon with a density proportional to the density of the subject at corresponding points and removing the non-adhering pigment.

2. The process according to claim 1 which includes the steps of applying to the image formed by the remaining pigment a synthetic resin and thereafter heat treating the work to set the resin as a durable coating upon the pigment and to form a strong bond between the pigment and supporting object.

3. The process according to claim 1 which includes the steps of applying to the image formed by the remaining pigment a synthetic resin of the urea-formaldehyde type and thereaftersettin the resin as a durable coating upon the pigment and to form a strong bond between the pigment and supporting object.

4. The process according to claim 1 which includes the step of applying a rotective, transparent coating to the ima e formed by the remaining pigment.

5. The process according to claim 1 which includes the step of applying a binder to the remaining film of pigment and causing said film to adhere to the object to be decorated or marked.

6. The process according to claim 1 which includes the step of heat treating the remaining film of pigment and the supporting object to cause said film to fuse with said object and form an integral part thereof.

7. The process according to claim 1 which includes the steps of coating the film of pigment with a binder comprising a lacquer containing nitrocellulose, dibutyl phthalate, China-wood oil and a solvent therefor.

8. The process according to claim 1 which includes the steps of transferring the film of pigment thus formed to a heat fusible object and thereafter heat treating said film to fuse the same with said object.

9. The process according to claim 1 which includes the steps of applyin to the film of pigment a binder comprising a lacquer of the long flexible type which is insoluble in water.

. KENNETH SMITH.

RUDOLPH ZERBST. 

